The present invention relates to an electrode holder suitable for use in making gates, sub-gates or other angled burns. In particular, this invention relates to a two-piece, pivotal gate electrode holder applied in electrical discharge machining (EDM) so as to eliminate time spent on producing temporary holders and allow installation of gates on any size mold.
Plastic parts, whether they be plastic spoons or dashboard components, are molded in plastic injection molds. Many times the mold produced to manufacture these parts have features in the cavity or the runner system that require EDM burning to be done on angles (for example sub-gates). A sub-gate is a feature that allows the plastic injected into the mold to get into the cavity region. Gates have typically been installed in molds either by 1) making a temporary holder out of inexpensive material incorporating the angle at which the gate is to be installed and then burning the gate into the mold or 2) tipping the mold at an angle to allow the burning process to be done in a purely xe2x80x9cZxe2x80x9d direction. The disadvantages of the above processes are that the temporary holder is usually discarded thereby wasting time and money in producing this temporary holder for one use and that tipping the mold is not practical when working with larger molds. The injected plastic gets into the mold cavity region by means of a gate.
These disadvantages are overcome by the two-piece holder joined by a common pivot point held in place by a holding means of the present invention. A variety of electrode holders for use in EDM have been disclosed in the relevant art but none of the references uncovered disclose or suggest the invention at hand.
U.S. Pat. No. 2,978,616, issued Apr. 4, 1961 to Pfau, discloses an electrode holder for use with an electroerosion machine, comprising a magnetic chuck having two circular discs of ferromagnetic material having flat end faces contacting each other, one of the discs being movable in the unmagnetized state and adapted to support the electrode, the other disc being stationary and having a first projection overlapping the movable disc and a second projection limiting the movement of the movable disc along the overlapping projection and defining the assembled position of the discs; and a means for creating a magnetic field holding the two discs in assembled position.
U.S. Pat. No. 3,614,370, issued Oct. 19, 1971 to Italo, discloses an electrode holder adapted to be used with an electric discharge machine which has an electrically conductive electrode, comprising a main housing that is generally annular to define a central opening having a central axis along which the electrode is fed during use; a base element rotatably supported by the main housing; an adjusting ring supported by the base element to be movable relative thereto; and electrically nonconductive guide rollers disposed symmetrically about the central axis to engage the electrode.
U.S. Pat. No. 4,319,115, issued Mar. 9, 1982 to Bonga, discloses an electrode tool holder for an EDM apparatus which can support either an electrode tool of large size or an electrode tool of small size, comprising an EDM apparatus with a ram consisting of two separate, linear moveably slide members, wherein one of the slide members carries a holder for an electrode tool of small dimension and wherein a second slide member is arranged to be coupled to the first slide member for supporting an electrode tool of large dimension.
U.S. Pat. No. 4,713,515, issued Dec. 15, 1987 to Choi, discloses an electrode holder for electric discharge processing machines that clamps the electrode in two perpendicular directions by clamp members, wherein each of the two clamp members slidably rests on a base seat which has side portions that extend at right angles to each other. The electrode holder disclosed in the ""515 reference does not allow for the electrode to be placed in a plurality of positions while the rotating head of the electrode holder of the present invention allows the electrode to be placed a variety of different positions.
U.S. Pat. No. 4,853,512, issued Aug. 1, 1989 to Scheider, discloses a spark erosion machining apparatus with an electrode changing mechanism having an electrode storage means and electrode support members, wherein the electrode storage means comprises linkage means pivotally connecting the electrode support members to at least one side wall of the tub of the machining apparatus and wherein the electrode support members are pivotal from a retracted rest position near said side wall of the tub into an operating position in which they protrude from the side wall of the tub towards the interior of the tub into an operating region. While the electrode support members of the ""512 patent are pivotal, the support member are pivotal only from the rest to the operating positions. In contrast, the rotating head of the present invention allows the electrode holder to be pivoted to a variety of operating positions.
U.S. Pat. No. 5,324,907 issued Jun. 28, 1994 to Wallace, discloses an EDM apparatus having a support base with adjustable slides mounted thereon; a cam arm mounted at one end on a piston rod that is used to cause vertical movement of the cam arm; a bore in the opposing end of the cam arm that rotatably receives a sleeve; and an electrode holder pivotally mounted in the sleeve such that one end of the electrode holder extends beyond the end of the sleeve, the electrode holder being movable between a first normal working position and a second non-working position that corresponds to movement of the cam arm. As in the ""512 reference, the ""907 reference only allows for pivoting the electrode holder between working and non-working positions, whereas the present invention provides for pivoting the electrode holder into a variety of working positions.
U.S. Pat. No. 5,791,803 issued Aug. 11, 1998 to Nordquist, discloses a compressive holding device serving as an electrode support having two coupling pieces and forcible elements for reversibly, axially, and compressively engaging the two coupling pieces in mutual engagement, where one of the coupling pieces has a plurality of aligning elements and the other coupling piece has a plurality of cooperating elements, and the aligning elements and/or cooperating elements are subjected to a force in the circumferential direction.
The object of the present invention is to provide a gate electrode holder that is reusable and compatible with a variety of mold sizes. A preferred embodiment of this invention is directed to a sub gate holder electrode holder for use in electric discharge machining (EDM).
This object is accomplished by the preferred embodiment of the present invention which provides for a sub gate electrode holder used in EDM comprising a stationary base having a first end and a second end; a rotating head having a first end and a second end, wherein the first end of the rotating head is pivotally positioned over the second end of the stationary base; two end caps affixable the second end of the stationary base; and a pocket positioned in the center of the second end of the rotating head for receiving an electrode.
The second end of the stationary base contains a spreader screw hole and a split. When a spreader screw is inserted and tightened into the spreader screw hole, the split allows the cylindrical end to flex, thereby securing the rotating head in the desired position to the cylindrical end of the stationary base. When the EDM process is complete, the spreader screw is removed, thereby releasing the stationary base from the rotating head and allowing the rotating head to be rotated into a new position for reuse.
The present invention also discloses an alternative preferred embodiment functioning exactly as the preferred embodiment but having a slightly different form in that the end caps are secured to the rotating head instead of the stationary base, and the rotating head has a slot as opposed to a pocket for receiving the electrode and has a plurality of screws (preferably five) for securing the electrode in place.